1. Technical Field
The embodiments herein generally relate to semiconductor processing, and more specifically, to wet etch and clean chemistries used in semiconductor processing.
2. Description of the Related Art
In order to achieve a high-k capacitor with an effective oxide thickness (EOT) less than 0.65 nm and a physical thickness less than 10 nm for the dielectric film of a dynamic random access memory (DRAM) device, very high-k, typically crystalline materials, are needed (i.e., k>50). As the value of k for the dielectric increases, the band gap (Eg) of the dielectric material is reduced and hence, the device leakage increases unfavorably. To counter the high leakage, electrodes made of sufficiently conductive materials with high work function and barrier heights are required to complement the high-k dielectrics used. Noble metal electrodes are typically the first option but given their high cost and common difficulties handling/processing them, they are not a practical solution for production. Conducting non-noble metal oxides (e.g., MoO2 because of its compelling lower cost than other material candidates and its ability to be safely processed) are interesting materials that could be used as the material is sufficiently conductive, and they can allow appropriate templating of the required crystallographic phase during the subsequent high-k deposition.
However, with the use of these new non-noble electrode systems in the manufacturing process of microelectronic products, new challenges arise as how to remove them from areas where their presence is undesirable. As an example, Mo being near noble (i.e. inert) is difficult to remove. As another example, trace amounts of these metals on the back side or bevel areas of the wafer can cause cross-contamination during production, typically mandating a suitable cleaning process to lower their surface concentrations to acceptable levels. Another example includes selective removal of the bulk electrode material during patterning of the deep sub-micron electric device capacitor feature for DRAM products. This can be accomplished by using a photoresist process or a hardmask process or any other known method for pattern transfer. The amount of material that is to be removed delineates the difference between wet etch (removing bulk material) and wet clean (removing trace amounts of material).
There remains a need to identify appropriate wet chemistries that are viable for DRAM production using non-noble materials such as MoO2 and that have a high capability of removing Mo and MoO2 from a silicon wafer during the manufacturing process using a wet chemistry process.